Practically, Tableau Desktop and Tableau Server takes better advantage of the capabilities of source databases to execute more queries at the same time. The goal of this Tableau “Parallel Queries" feature is to improve Dashboard performance, on Desktop and Server.
Prior to version 9.0, Tableau Desktop and Tableau Server maintained a single connection per data source, and would send all queries sequentially. With serial query processing, the elapsed time for executing all queries against a data source was equal to or greater than the sum of the elapsed time for each individual query execution. Parallel queries in Tableau Server and Tableau Desktop must first be configured, but once they are configured, the feature is automatically on.
Please note that parallel queries will run only when possible. In other words, if a query is based on a field already queried, then the parallel query will not run and will wait until the previous query will end.
The parallel queries will run in parallel only if there are not concurrent queries on the same field/table.
Simply put, enabling parallel queries can impact the performance of Tableau Desktop. For example, if too many queries (or resource-intensive queries) are happening in parallel, the performance may be slower than expected. It would be ideal to discuss any configuration changes with your Tableau Server administrator and/or internal IT team before doing so, as they are more familiar with your environment.
Parallel queries can be configured in both Tableau Desktop, and Tableau Server.
For more information on configuring parallel queries in Tableau Desktop and Tableau Server, please review the articles below.
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